There are presented the results of investigations on determination of the effect of wheel passage number, tyre inflation pressure and wheel load on soil compaction. Investigations were carried out in a soil bin filled with the fine loamy soil layer of dimensions 10 x 2 x 1 m (length x width x depth), of moisture content 12%. In investigations there was used the tractor wheel with tyre 7.50 - 16, loaded with axial forces 3,600 and 5,199 N and rolled on the measuring length 1-2—1-8 times at speed 0.82 m/s. The investigations showed a highly significant effect of wheel passage number, tyre inflation pressure and depth of measurement on compaction values in soil profile under the wheel track. In the range of applied wheel loads and tyre inflation pressures, the highest changes in soil compaction were found in the superficial layer - up to 0.05 m.
This paper presents results of the researches carried out in 1996-1998 in Mydlniki on silty soil. Results showed that multiple passes of tractor wheels changed air and water properties of the soil under grasslands. The useful and productive retention decreases in accordance to number of passes. This is a result of the decrease of the field water capacity connected with large pores. These changes are observed in every layer of the investigated soil, but the largest differences are noticed in 0-5 cm layer.